It is planned during the coming year to continue to apply our metabolic model for sulfite to the estimation of the risk of different species to sulfite toxicity and to extend its application to newborn and young animals. Distribution of protein S-sulfonate in tissues other than the plasma will be investigated with the aid of 35S tracer to increase the sensitivity and accuracy of the analytical method. The role of cysteine-S-sulfonate as a carrier molecule for sulfite by virtue of the reversibility of S-sulfonate formation and SS--SH interchange reactions will also be further investigated. In addition, the possibility of systematic sulfite toxicity will continue to be pursued emphasizing the possible toxic effect of sulfite on rabbit oocytes.